Take care of outside house plants

As we move toward October, it’s not too early to make plans for houseplants that spent the summer outdoors. You will need to bring them back inside at some point when it starts to get cold. But you have a variety of jobs to do now.

After a summer of growth, some of your container plants may have become pot-bound. Finish up any repotting you need to do in October so plants will have a chance to recover before being brought back inside. And think carefully about pot size before you repot the plant. If you shift the plant into a larger container, will it still be convenient to move inside? Or will the larger pot make the plant unwieldy and too heavy to move easily?

Here’s a way of dealing with a pot-bound plant and keeping it in the same size pot. First, remove the plant from the pot and trim off one-quarter to one-third of the lower part of the root ball. Put a layer of fresh potting mix equal to the volume of root ball removed in the bottom of the original container. Place the plant back in the pot, adding a little more soil around the sides if necessary. Water it well, and place the plant in a shady location to recover.

Use a good-quality potting mix when repotting. Gardeners generally rely on commercially available potting-soil mixes for growing most types of houseplants. Many brands are out there, however, and not all of them are especially good. In particular, avoid heavy, black potting soils. If the bag feels dense and heavy for its size, put it back. The best potting mixes include peat moss, vermiculite, bark and perlite in proportions that create a fairly light, loose mix that water readily penetrates and rapidly drains from.

Finish up any pruning this month. Look at the size of your plants and imagine them coming inside. If their size needs to be reduced, do it now so they will have time to make some new growth under favorable growing conditions before going indoors.

Houseplants also need to be acclimated to lower light conditions before they are moved back inside. Light conditions are not as bright indoors as they are outside. Houseplants growing in sunny or partly sunny locations should be moved to shady areas by early October. This will help them adjust to the lower light conditions they will receive when they are moved inside in early to mid-November.

When moved indoors, most houseplants that summered outside will need all the light they can get. Windows obstructed by hedges, tree branches and screens allow less light to enter. If they need more light, trim hedges and tree branches to allow more light to enter. Screens could be removed from windows that are not normally opened to let in fresh air. Even washing a window can remove dust and grime that cut down on the amount of light.

Houseplants that spent the summer outside should also be groomed so they will look their best. And you’ll be less likely to bring pests inside with the plants.

When it’s time to bring the plants indoors, consider these steps:

Clean the outside of containers using a brush and a mild solution of dishwashing liquid and water. Add a little bleach to the solution to kill algae growing on the pot sides. Avoid getting this solution in the soil.

Remove dust and debris from the foliage and where leaves join the stems. Hose down the plants and wipe the foliage clean with a soft damp cloth.

Remove all dead or yellow foliage, old flower stalks and dead or injured branches and stems.

Pests have had all summer to infest and build up populations on your outside houseplants. You definitely want to take care of all of those problems before you bring plants inside for the winter. If pest control is necessary, it is far better and more convenient to use pesticides outside rather than indoors. Begin to inspect plants carefully looking for signs of scale, snails and slugs, caterpillars, spider mites, aphids or mealybugs. Pull any weeds that may have found their way into pots. Prune off any badly damaged leaves or growth.

Control scale, spider mites, aphids and mealybugs with several applications of a light horticultural oil, such as Year Round Spray Oil or All Seasons Spray Oil. Make sure to coat the plant thoroughly with the spray, getting under the leaves and into where they join the main stem. Oil sprays kill insects by coating and suffocating them rather than by the action of toxic substances, so complete coverage is important.

Any caterpillars you find can generally be handpicked and disposed of, but you could also treat your plants with a Bt insecticide or spinosad.

Snails and slugs love to hide under pots on patios, porches and decks during the day. Regularly tip over the pots, check for snails and slugs, and remove those you find.

Be on the lookout for critters such as frogs, toads and lizards that may hitch a ride inside with the plants. These beneficial animals should be carefully removed and released unharmed outside.

With a little effort now, you can get these jobs out of the way and not feel so rushed when cold weather arrives and protecting the plants becomes the main concern.

Dan Gill is a horticulturist with the LSU AgCenter. He can be reached at DGill@agcenter.lsu.edu

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